To meet the demand for wireless data traffic having increased since deployment of 4G communication systems, efforts have been made to develop an improved 5G or pre-5G communication system. Therefore, the 5G or pre-5G communication system is also called a ‘Beyond 4G Network’ or a ‘Post LTE System’. The 5G communication system is considered to be implemented in higher frequency (mmWave) bands, e.g., 60 GHz bands, so as to accomplish higher data rates. To decrease propagation loss of the radio waves and increase the transmission distance, the beamforming, massive multiple-input multiple-output (MIMO), Full Dimensional MIMO (FD-MIMO), array antenna, an analog beam forming, large scale antenna techniques are discussed in 5G communication systems. In addition, in 5G communication systems, development for system network improvement is under way based on advanced small cells, cloud Radio Access Networks (RANs), ultra-dense networks, device-to-device (D2D) communication, wireless backhaul, moving network, cooperative communication, Coordinated Multi-Points (COMP), reception-end interference cancellation and the like. In the 5G system, Hybrid FSK and QAM Modulation (FQAM) and sliding window superposition coding (SWSC) as an advanced coding modulation (ACM), and filter bank multi carrier (FBMC), non-orthogonal multiple access (NOMA), and sparse code multiple access (SCMA) as an advanced access technology have been developed.
The Internet, which is a human centered connectivity network where humans generate and consume information, is now evolving to the Internet of Things (IoT) where distributed entities, such as things, exchange and process information without human intervention. The Internet of Everything (IoE), which is a combination of the IoT technology and the Big Data processing technology through connection with a cloud server, has emerged. As technology elements, such as “sensing technology”, “wired/wireless communication and network infrastructure”, “service interface technology”, and “Security technology” have been demanded for IoT implementation, a sensor network, a Machine-to-Machine (M2M) communication, Machine Type Communication (MTC), and so forth have been recently researched. Such an IoT environment may provide intelligent Internet technology services that create a new value to human life by collecting and analyzing data generated among connected things. IoT may be applied to a variety of fields including smart home, smart building, smart city, smart car or connected cars, smart grid, health care, smart appliances and advanced medical services through convergence and combination between existing Information Technology (IT) and various industrial applications.
In line with this, various attempts have been made to apply 5G communication systems to IoT networks. For example, technologies such as a sensor network, Machine Type Communication (MTC), and Machine-to-Machine (M2M) communication may be implemented by beamforming, MIMO, and array antennas. Application of a cloud Radio Access Network (RAN) as the above-described Big Data processing technology may also be considered to be as an example of convergence between the 5G technology and the IoT technology.
The mobile communication system has evolved into a high-speed, high-quality wireless packet data communication system to provide data and multimedia services beyond the early voice-oriented services. In line with this tendency, the standardization organizations such as 3rd Generation Partnership Project (3GPP), 3GPP2, and Institute of Electrical and Electronics Engineers (IEEE) are standardizing 3G evolved mobile communication standards based on multicarrier multiple access scheme. The 3GPP Long Term Evolution (LTE), 3GPP2 Ultra Mobile Broadband (UMB), and IEEE 802.16m are the mobile communication standards that have been developed to support high speed high quality wireless packet data communication services based on the multicarrier multiple access scheme.
Existing 3G evolved mobile communication standards such as LTE, UMB, and IEEE 802.16m based on the multicarrier multiple access scheme are characterized by various techniques including Multiple Input Multiple Output (MIMO), beamforming, Adaptive Modulation and Coding (AMC), channel sensitive scheduling, etc. for improving transmission efficiency. Such techniques are capable of concentrating transmission power with multiple antennas or adjusting transmission data amount depending on the channel quality and transmitting data to the user with good channel quality selectively, resulting in improvement of transmission efficiency and increase of system throughput.
Because most of these techniques operate based on the channel state information between an evolved Node B (eNB) (or Base Station (BS)) and a User Equipment (UE) (or Mobile Station (MS)), the eNB or UE has to measure the channel state between the eNB and UE based on Channel State Indication Reference Signal (CSI-RS). The eNB is a transmitter in downlink and a receiver in uplink and capable of managing a plurality cells for communication. A mobile communication system is made up of a plurality of eNBs distributed geographically, and each eNB manages a plurality of cells to provide the UEs with communication service.
Existing 3G and 4G mobile communication systems represented by LTE/LTE-A adopt MIMO techniques using a plurality of transmission/receive antennas to increase data rate and system throughput. Using a MIMO scheme, it is possible to transmit a plurality of information streams separated spatially. This technique of transmitting the plural information streams is referred to as spatial multiplexing. Typically, the number of information streams to be spatially multiplexed is determined depending on the numbers of antennas of the transmitter and receiver. The number of information streams that can be spatially multiplexed is referred to as rank of the corresponding transmission. The LTE/LTE-A Release 11 supports 8×8 MIMO spatial multiplexing and up to rank 8.
The Full Dimension MIMO (FD-MIMO) system equipped with the technology proposed in the present invention is capable of utilizing 32 or more transmit antennas as compared to the legacy LTE/LTE-A MIMO technology supporting up to 8 antennas.
In the present invention, the FD-MIMO system denotes a wireless communication system capable of transmitting data using a few dozen or more of transmit antennas.
There is therefore a need for a method for a terminal to measure the channels between the base station and the terminal with low overhead and report the channel state information generated based on the measurement result to the base station efficiently.